Slow Cooker Cheesy Potato Casserole

Frozen Southern Style Hash Brown Potatoes (2 (12oz) bags)

Frozen Minced Onions (2 tsbp)

Sour Cream (2 cups)

Cream of Chicken Soup (1 can)

Butter (melted, 1/2 cup)

Salt (1tsp)

Shredded Cheddar Cheese (3 cups divided)